The present invention relates to an adsorption unit with pressure modulation (Pressure Swing Adsorption or PSA), of the type comprising 2N adsorbers (Nxe2x89xa72) each having a production outlet. It is applicable particularly to the production of hydrogen, methane or CO by PSA adsorption.
The PSA cycles comprise successively, for each adsorber: a production phase by adsorption; a regeneration phase of the adsorbent comprising at least one step of co-current depressurization with pressure balancing with another adsorber, a step of final counter-current depressurization with evacuation of residual gas, and generally an elution step at the low pressure of the cycle; and a repressurization phase comprising at least one pressure balancing step with another adsorber, and a final repressurization step by means of production gas.
In what follows, there will be meant by xe2x80x9cinletxe2x80x9d and xe2x80x9coutletxe2x80x9d of an adsorber, the inlet of the gas to be treated and the outlet of the product gas during the step of production of the PSA cycle, by xe2x80x9cco-currentxe2x80x9d the direction of circulation of the inlet toward the outlet, and by xe2x80x9ccounter-currentxe2x80x9d the reverse direction of circulation. Moreover, the pressures indicated are absolute pressures.
In conventional PSA units of the mentioned type, there is provided for each step of the cycle (production, pressure balancing between adsorbers, counter-current depressurization, elution, final repressurization) a transverse line common to all the adsorbers, which can be connected individually to the outlet of each adsorber by means of a corresponding valve.
Correspondingly, when the unit comprises a large number of adsorbers, as is often the case in hydrogen production installations, each adsorber is associated with as many valves as there are transverse lines. This leads to an extremely complex and costly tubing, both from the point of view of capital cost and from that of maintenance or size.
The invention has for its object considerably to simplify the tubing of the PSA unit.
To this end, the invention has for its object a PSA adsorption unit of the mentioned type, characterized in that:
the adsorbers are coupled in the form of adsorber pairs;
the outlets of the adsorbers of each pair are connected by a direct line provided with two first valves; and
an intermediate point of the direct line located between the two first valves is connected to a transverse line common to all the pairs by means of a connection valve.
The PSA adsorption unit according to the invention can comprise one or several of the following characteristics, taken alone or in their various possible technical combinations:
the adsorbers being numbered in their order of passage to the production phase in the course of each cycle, the adsorber couples are A1-AN+1, A2-AN+2, . . . , Ai-AN+i, . . . , AN-A2N,
at least two of said intermediate points are connected by a connection line provided with a second connection valve,
the two first valves are control valves whilst the connection valves are open-shut valves,
said intermediate point is moreover connected to the common transverse line by a supplemental connection line provided with a supplemental connection valve which is a control valve,
the unit moreover comprises at least one additional transverse line connected individually to the outlet of each adsorber via a control valve,
at least one additional transverse line can be subdivided, by manipulating an additional valve, into two transverse half-lines each connected to N adsorbers,
at least one additional transverse line is subdivided into two transverse half-lines, of which each is connected to N adsorbers,
the adsorbers contain at least one adsorbent adapted to the production of hydrogen, methane or CO, typically active carbon and/or zeolite and/or activated alumina.